1. Field of the Invention
The present invention relates to a method of forming GaAs/AlGaAs hetero-structure and GaAs/AlGaAs hetero-structure obtained by the method.
2. Description of the Related Art
Conventionally, MBE (molecular beam epitaxy) growth of GaAs or AlGaAs layer on GaAs substrates has been done on the (100) surface. While the superiority of optical and electronic properties of the semiconductor layer grown on the (100) surface has been demonstrated by the success of various devices such as a laser device or HEMT (high electron mobility transistor), in recent years, growth on other surfaces than the (100) surface have also been attempted with various motivations.
However, GaAs/AlGaAs hetero-structures grown on the (100) surface have room for improvement in the atomic flatness of hetero-interfaces, and this leads to rather unsatisfactory results in their optical and electrical properties.
GaAs/AlGaAs quantum wells grown on GaAs (100) substrates with the growth interruption show much narrow luminescence peaks in PL spectra. Existence of one-monolayer atomic steps at the hetero-interfaces of the quantum wells (well width of Lo) grown with the growth interruption, however, results in three kinds of wells with different thicknesses (Lo, Lo.+-.1 ML) laterally coexisting in an area excited by a laser beam which leads to three luminescence peaks in the PL spectra for a single quantum well. It is still difficult to eliminate this atomic step structure at the interface even by the growth interruption technique. Dimension of island by this atomic step at the GaAs/AlGaAs interface is around several um as determined by scanning cathodoluminescence technique. This atomically flat area is much smaller than a contact area of a semiconductor hetero-structure device, so it has been difficult to use an atomically flat interface in real devices.
Taking the above-described state of the art into consideration, a primary object of the present invention is to provide a method of forming GaAs/AlGaAs layer with much improved hetero-interface, which results in further improved optical and electrical properties.